/*
 * Copyright (c) 2017 Baidu, Inc. All Rights Reserve.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.baidu.fsg.uid.utils;

import java.net.InetAddress;
import java.net.NetworkInterface;
import java.net.SocketException;
import java.util.Enumeration;

/**
 * NetUtils
 *
 * @author yutianbao
 */
public final class NetUtils {
	/**
	 * Pre-loaded local address
	 */
	private static InetAddress localAddress;

	static {
		try {
			localAddress = getLocalInetAddress();
		} catch (SocketException e) {
			throw new RuntimeException("fail to get local ip.", e);
		}
	}

	private NetUtils() {
	}

	/**
	 * Retrieve the first validated local ip address(the Public and LAN ip addresses are validated).
	 *
	 * @return the local address
	 * @throws SocketException the socket exception
	 */
	public static InetAddress getLocalInetAddress() throws SocketException {
		// enumerates all network interfaces
		Enumeration<NetworkInterface> enu = NetworkInterface.getNetworkInterfaces();

		while (enu.hasMoreElements()) {
			NetworkInterface ni = enu.nextElement();
			if (ni.isLoopback()) {
				continue;
			}

			Enumeration<InetAddress> addressEnumeration = ni.getInetAddresses();
			while (addressEnumeration.hasMoreElements()) {
				InetAddress address = addressEnumeration.nextElement();

				// ignores all invalidated addresses
				if (address.isLinkLocalAddress() || address.isLoopbackAddress() || address.isAnyLocalAddress()) {
					continue;
				}

				return address;
			}
		}

		throw new RuntimeException("No validated local address!");
	}

	/**
	 * Retrieve local address
	 *
	 * @return the string local address
	 */
	public static String getLocalAddress() {
		return localAddress.getHostAddress();
	}

}
